The "Snorkel" is the longer tube that allows you to breath while being face down swimming around the ocean.
What You Should Look For in a Snorkel
Dry snorkel – "Dry" snorkels have a splash proof opening at the top of the Snorkel and a one way water purge valve at the bottom. The splash proof top section helps to reduce the water flowing into the opening and into your mouth. The purge valve is for flushing out water that has entered the mask when you exhale. This invention and addition to the snorkel is a huge improvement over traditional snorkels where you were in constant risk of taking in a stomach full of salt water with your next breath.
You should try to avoid snorkels where the splash guard operates via some type of moving mechanical contraption. Quite often, the moving parts in these mechanisms become stuck and jam when sand gets into them. It's only a matter of time before these moving (usually cheaply made parts) will cause you problems. Some snorkekls have a real simple "splash guard" which works like your chimney rain guard; a means to guide the incidental splash water away from the snorkel opening.
Large diameter tube – As a general rule, the larger diameter of a tube allows more air volume as well as makes for easier air flow during breathing. The more air for you to breathe, the more capacity for your lungs to utilize while swimming.
A comfortable mouth piece – Usually this is not a problem, but if you’re renting and/or especially if you’re purchasing, definitely make sure that your snorkel is comfortable within your mouth. You should not have to use your teeth to keep your snorkel from popping out of your mouth. A well fitting or adjusted snorkel should sit comfortably in your mouth and should stay where its at when you jaw is relaxed.
Rigid or flex – All Snorkels will have either have a flexible or rigid bend at the bottom of the tube adjacent to the mouth piece. The flexible snorkel tube type allows for some adjustment when the angle of the snorkel mouth piece doesn’t line up with the attachment point on the mask strap. When the angle isn’t quite right with the snorkel tube, it will twist constantly or stay twisted in your mouth (making you uncomfortable.) This problem can be fixed by taking a moment to get the proper position on the snorkel before jumping into the water. Its all a matter of personal preference (Flexible or Rigid). Get the type that’s most comfortable for you when you are trying it on. …
To Avoid Any Unforseen Problems
Definitely try your snorkel on with the actual mask that you will be using – This is because all snorkel masks have variations in them when it comes to their shape, buckle placement, etc. After trying both Snorkel and the Snorkel Mask on together